Many polymeric materials often present fire hazards due to their highly combustible nature. Usually, this is related to their chemical structures, which, in many polymers, consist mostly of hydrogen and carbon (see Laoutid, F. et al., MATERIALS SCIENCE AND ENGINEERING: R: REPORTS 63(3) 2009, 100-25). Therefore, it is desirable to improve the fire performance of these materials—especially for various applications where fire safety is a concern.
Generally, improvements in fire performance may be achieved by reducing the availability of one or more of the essential elements that sustain the combustion cycle (i.e., the fire triangle): combustibles (reducing agent, typically organic volatiles from decomposition of the polymer), combustives (oxidizing agent, typically oxygenation in air), and heat.
Previous research has demonstrated that when applied to the surface of polymer matrix composites, carbon nanotube (CNT) buckypapers may serve as an effective fire retardant shield and may reduce fire hazard (see Wu, Q. et al., CARBON 46(8) 2008, 1164-5; Wu, Q. et al., CARBON 48(6) 2010, 1799-806). Buckypapers are thin membranes that may consist of a dense network of entangled CNT ropes (see Liu, J. et al., SCIENCE 280(5367) 1998, 1253-6). It is believed that buckypapers have some fire retardancy because buckypapers may reduce the transport of both combustibles and combustives. The dense network of nonflammable CNTs may act as a physical barrier to the diffusion of oxygen, and may slow the escape of combustion products from the decomposition of the polymer matrices. Previous results have shown that pure, unmodified multi-walled carbon nanotube buckypapers, when used as a fire shield, increase the time to ignition (TTI) of an epoxy/carbon fiber composite from 46 to 64 seconds (see Wu, Q. et al., CARBON 48(6) 2010, 1799-806). There is a need, however, to improve the existing buckypaper fire shields.
Magnesium hydroxide (MDH) particles have some fire retardant capability. In the past, MDH particles have been utilized as a fire retardant additive by being incorporated in a polymer matrix as a filler (see Huang, H., et al., J. APPL. POLY. SCI. 100(6), 2006, 4461-9; Gui, H. et al., POLYMER 48(9), 2007, 2537-41; Gui, H., et al., COMPOSITES SCI. & TECH. 67(6), 2007, 974-80; Lv., et al., J. APP. POLY. SCI. 105(2), 2007, 333-40). Nano-sized MDH particles have been shown to be more effective as compared to larger particle sizes (see Huang, H., et al., J. APPL. POLY. SCI. 100(6), 2006, 4461-9). However, these known methods require high-weight loading (generally more than 60%) to achieve satisfactory fire retardancy. This high-weight loading often is undesirable—especially since the high concentration of particles may give rise to processing issues and/or deteriorate the mechanical properties of composites (see Wang, J. et al., J. APP. POLY. SCI. 60(9), 1996, 1425-37).
Therefore, fire retardant materials that overcome at least one or all of the above-described disadvantages are desirable.